Image forming apparatus and method for detecting amount of remaining toner

0001This non-provisional application claims priority under 35 U.S.C. § 119(a) on Patent Application No. 2005-264473 filed in Japan on Sep. 12, 2005, the entire contents of which are hereby incorporated by reference.

FIELD OF THE INVENTION

0002The present invention relates to an image forming apparatus, forming images by use of toner, which is capable of exactly detecting the amount of remaining toner until the toner runs out.

BACKGROUND OF THE INVENTION

0003In an image forming apparatus for forming images by use of toner, such as a printer, a copying machine, and a facsimile, it is necessary to grasp the amount of remaining toner for convenience of maintenance such as toner supply.

0004However, in a case where an image forming apparatus is provided with a remaining toner detection device, the cost inevitably increases. Therefore, there has been used a technique in which the amount of remaining toner is detected by use of existing members.

0005For example, Japanese Unexamined Patent

0006Publication No. 221944/1998 (Tokukai 10-221944; published on Aug. 21, 1998) discloses a technique in which: when two-component developer is used, the amount of remaining toner is detected based on the result of Auto Toner Control (ATC).

0007ATC is a method for controlling toner density of developer so that the toner density is constant based on magnetic permeability of the developer. Two-component developer is constituted of (i) carrier made of iron powder and the like and (ii) toner with predetermined density (e.g. 4 to 5%). As such, when toner in the developer is used and the ratio of carrier increases, the magnetic permeability of the developer increases. Therefore, by detecting the magnetic permeability of the developer, it is possible to grasp the ratio of toner in the developer.

0008Examples of ATC include (i) a technique in which: when magnetic permeability rises and exceeds an upper limit (corresponding to a lower limit of toner density), a supply motor is rotated for a predetermined time (alternatively, predetermined number of rotations) and toner is supplied from a toner supply source such as a toner bottle, and (ii) a technique in which: a lower limit of magnetic permeability (corresponding to an upper limit of toner density) is previously set and when the magnetic permeability rises and exceeds an upper limit, a supply motor is rotated until the magnetic permeability falls to the lower limit, thereby supplying toner from the toner supply source.

0009In either technique, as the amount of remaining toner in the toner supply source drops, the effect of drop appears in ATC. The result of ATC allows detection of the amount of remaining toner. Namely, in the technique (i), the amount of toner supply per a predetermined time for rotating the supply motor is reduced, so that toner supply is frequently repeated, which makes it possible to detect that the amount of remaining toner is small. Further, in the technique (ii), the amount of toner supply per a predetermined time for rotating the supply motor is reduced, so that the time for toner supply (time taken for the magnetic permeability to fall to the lower limit) becomes long, which makes it possible to detect that the amount of remaining toner is small.

0010Thereafter, when the supply motor is rotated for a predetermined time (e.g. 3 seconds) but the magnetic permeability does not have the former value, namely, when the toner density does not increase, toner empty (toner run out, toner end) is detected.

0011Further, examples of a conventional technique for detecting the amount of consumed toner or remaining toner by use of existing members other than ATC are as follows.

0012Japanese Unexamined Patent Publication No. 163553/2004 (Tokukai 2004-163553; published on Jun. 10, 2004) discloses a technique in which: the number of formed printing dots is counted, the counted number is multiplied by a predetermined weight coefficient, thus multiplied number is accumulated and, based on thus accumulated number, the amount of toner consumption is obtained. Further, Japanese Unexamined Patent Publication No. 163553/2004 discloses that the weight coefficient is modified according to the history of toner use.

0013Further, Japanese Unexamined Patent Publication No. 163554/2004 (Tokukai 2004-163554; published on Jun. 10, 2004) discloses a technique in which the amount of remaining toner is obtained in such a manner that (i) the number of printing dots is counted based on image signals and the amount of toner consumption is calculated based on the counted number, and (ii) in an operation mode such as a density control mode which includes formation of a patchwork image, the amount of toner consumption is calculated according to a pattern of the patchwork image.

0014Further, Japanese Unexamined Patent Publication No. 333419/1998 (Tokukaihei 10-333419; published on Dec. 18, 1998) discloses a technique in which: a toner supply function for converting a video count value of an image in to a time for toner supply is corrected while being weighted by a video count value of an image under formation, and thus the amount of toner supply is corrected so as to correspond to the amount of toner consumption.

0015However, the conventional techniques for detecting the amount of remaining toner by use of existing members have the following problems to be solved.

0016For example, in the technique disclosed in Japanese Unexamined Patent Publication No. 221944/1998 for detecting the amount of remaining toner by carrying out ATC, it is impossible to chronologically detect the amount of remaining toner from a time when the toner is fully contained to a time when the toner runs out. Hence there is not an enough time for a user to prepare toner to be subsequently used, so that the operation rate of the image forming apparatus drops.

0017Namely, in ATC, it is not until the amount of remaining toner is much reduced that toner supply is frequently repeated or that it takes much time to supply toner per each supply. When the amount of remaining toner is much reduced, the number of printable sheets is only 50 to 100 (the number depends on the size of a sheet and a printing ratio). As a result, though a user is informed that the amount of remaining toner is small at a time when such state is detected, it is much likely that the toner runs out before next toner is prepared, resulting in that the image forming apparatus is stopped.

0018On the other hand, in the techniques not using ATC, disclosed in Japanese Unexamined Patent Publication No. 163553/2004, Japanese Unexamined Patent Publication No. 163554/2004, and Japanese Unexamined Patent Publication No. 333419/1998, the amount of toner to be used is exactly calculated based on image signals or patterns of patchwork images, and is regarded as the amount of toner consumption. Therefore, by obtaining the amount of remaining toner based on thus obtained amount of toner consumption, it is possible to detect that the amount of remaining toner is small before ATC does so that the detection result is informed to the user.

0019However, the actual amount of toner on a photoconductor is not constant because of the environment or variations in devices. Therefore, even though the amount of remaining toner is more exactly detected based on weighting or the like, it is difficult to determine whether toner runs out or not based only on the result of weighting.

0020Therefore, even though the user is informed that the amount of remaining toner is small under a condition that enough sheets are provided so as to be printed, toner may run out before a predetermined number of sheets are printed or toner may be judged to run out while the toner still remains.

SUMMARY OF THE INVENTION

0021The present invention was made in view of the foregoing problems. An object of the present invention is to provide an image forming apparatus and a method for detecting the amount of remaining toner, each of which allows exact detection of the amount of remaining toner without providing a device specially used to detect the amount of remaining toner. Another object of the present invention is to provide an image forming apparatus capable of informing a user of information concerning toner at a suitable timing based on the detected amount of remaining toner.

0022In order to achieve the foregoing object, the image forming apparatus according to the present invention is an image forming apparatus, which uses two-component developer constituted of toner and carrier and includes a toner density control section for supplying the toner from a supply device to a developing device on the basis of magnetic permeability of the developer so as to cause toner density in the developing device to be constant, the image forming apparatus comprising a remaining toner amount detection section for detecting the amount of remaining toner in the supply device, wherein the remaining toner amount detection section includes: a toner supply amount calculation section for calculating the amount of toner supply on the basis of the accumulated number of rotations of a supply motor which is rotated so as to supply toner from the supply device to the developing device; a toner consumption amount calculation section for calculating the amount of toner consumed by forming an image on the basis of image information; and the toner density control section, and the remaining toner amount detection section detects the amount of remaining toner on the basis of (i) the result of calculation carried out by the toner supply amount calculation section till the amount of remaining toner in the supply device reaches a first predetermined value, (ii) the result of calculation carried out by the toner consumption amount calculation section from a time when the amount of remaining toner in the supply device reaches the first predetermined value till the amount of remaining toner in the supply device reaches a second predetermined value, and (iii) the result of control carried out by the toner density control section from a time when the amount of remaining toner in the supply device reaches the second predetermined value.

0023With the arrangement, the amount of remaining toner in the supply device is detected on the basis of (i) the amount of toner supply which is calculated by the toner supply amount calculation section based on the accumulated number of rotations of the supply motor till the amount of remaining toner in the supply device reaches the first predetermined value, (ii) the amount of toner consumption which is calculated by the toner consumption amount calculation section based on the image information from the time when the amount of remaining toner in the supply device reaches the first predetermined value till the amount of remaining toner in the supply device reaches the second predetermined value, and (iii) the result of control carried out by the toner density control section from the time when the amount of remaining toner in the supply device reaches the second predetermined value.

0024Namely, the amount of remaining toner is detected based on the accumulated number of rotations of the toner motor in a region where the amount of remaining toner in the supply device is a predetermined amount or more and changes linearly in accordance with the number of rotations or the rotational time of the supply motor, resulting in the stabilized amount of toner supply. Further, the amount of remaining toner is detected by expecting the amount of consumed toner based on the image information in a region where the amount of remaining toner in the supply device gets small and the amount of toner supply gets uneven. Further, the amount of remaining toner is detected by using the result of control carried out by the conventional toner density control section in a region where the amount of toner is near end.

0025As a result, it is possible to detect the amount of remaining toner according to actually remaining toner, and accordingly it is possible to exactly detect the amount of remaining toner from a time when toner is fully contained to a time when toner runs out without providing a special remaining toner detection device.

0026Further, unlike the detection carried out only by ATC with respect to the amount of remaining toner, it is possible to chronologically detect the amount of remaining toner from a time when toner is fully contained to a time when toner runs out, so that it is easy to inform the user of information regarding toner at a suitable timing.

0027The image forming apparatus according to the present invention further includes an informing section for causing a display section to inform a user that preparation of toner is necessary, and the informing section causes the display section to inform the user that preparation of toner is necessary when detection carried out by the remaining toner amount detection section with respect to the amount of remaining toner shows that the amount of remaining toner in the supply device reaches a third predetermined value which is set in accordance with the amount of used toner per days taken for the user to obtain a supply device for exchange.

0028With the arrangement, when the amount of remaining toner reaches the third predetermined value which is set in accordance with the amount of used toner per days taken for the user to obtain the supply device for exchange, the informing section causes the display section to urge preparation of toner, so that the user can prepare the next toner at a suitable timing and accordingly it is possible to prevent reduction of the operation rate of the image forming apparatus.

0029The method according to the present invention for detecting the amount of remaining toner is a method for detecting the amount of remaining toner in a supply device applied to an image forming apparatus that uses two-component developer constituted of toner and carrier and that includes a toner density control section for supplying toner from the supply device to a developing device on the basis of magnetic permeability of the developer so as to cause toner density in the developing device to be constant, the method comprising the steps of: (i) detecting the amount of remaining toner in the supply device on the basis of the accumulated number of rotations of a supply motor which supplies the toner from the supply device to the developing device; (ii) detecting the amount of remaining toner in the supply device on the basis of the amount of toner consumed by forming an image on the basis of image information; and (iii) detecting the amount of remaining toner in the supply device on the basis of the result of control carried out by the toner density control section, wherein the method performs the step (i) when the amount of remaining toner in the supply device is large and changes linearly in accordance with the accumulated number of rotations of the supply motor, the method switches to the step (ii) when the amount of remaining toner in the supply device reaches a region where the amount is small and does not change linearly in accordance with the accumulated number of rotations of the supply motor, and the method switches to the step (iii) when the amount of remaining toner reaches a region where the amount is substantially 0.

0030In the method for detecting the amount of remaining toner as well as in the image forming apparatus already explained above, it is possible to detect the amount of remaining toner according to actually remaining toner, and accordingly it is possible to exactly detect the amount of remaining toner from a time when toner is fully contained to a time when toner runs out without providing a special remaining toner detection device and it is possible to inform the user of information concerning toner at a suitable timing.

0031Note that, the present invention may be realized by a computer. In that case, (i) a remaining toner detection program for causing a computer to function as sections included in the image forming apparatus according to the present invention and (ii) a computer-readable storage medium for storing the program, are also within the scope of the present invention.

0032For a fuller understanding of the nature and advantages of the invention, reference should be made to the ensuing detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

0033<figref idref="DRAWINGS">FIG. 1</figref> is a functional block diagram illustrating an essential structure of an image forming apparatus according to an embodiment of the present invention.

0034<figref idref="DRAWINGS">FIG. 2</figref> illustrates a longitudinal section of the image forming apparatus.

0035<figref idref="DRAWINGS">FIG. 3</figref> is a graph illustrating a relation between the amount of remaining toner in a toner bottle and the amount of toner falling from the toner bottle.

0036<figref idref="DRAWINGS">FIG. 4</figref> is a graph illustrating a relation between rotational time of a toner motor and the amount of remaining toner in the toner bottle.

0037<figref idref="DRAWINGS">FIG. 5</figref> schematically illustrates (i) switching of methods for detecting the amount of remaining toner by a remaining toner amount detection section and (ii) timing at which a remaining amount informing section causes the amount of remaining toner and information concerning the amount of remaining toner to be displayed.

0038<figref idref="DRAWINGS">FIG. 6</figref> is a control block diagram illustrating an image process carried out by the image forming apparatus.

0039<figref idref="DRAWINGS">FIG. 7</figref> illustrates contents of a weight coefficient table.

0040<figref idref="DRAWINGS">FIG. 8</figref> illustrates a relation between a signal input value and the amount of toner consumption, and a relation between the signal input value and a weight coefficient.

0041<figref idref="DRAWINGS">FIG. 9</figref> is a flowchart illustrating a procedure of the image forming apparatus, in which the amount of remaining toner is detected and a user is informed of information indicative of the amount of remaining toner based on the result of the detection.

0042<figref idref="DRAWINGS">FIG. 10</figref> is a flowchart illustrating a procedure of the image forming apparatus, in which the amount of remaining toner is detected and a user is informed of information indicative of the amount of remaining toner based on the result of the detection.

0043<figref idref="DRAWINGS">FIG. 11</figref> is an oblique view illustrating a toner bottle provided in the image forming apparatus.

DESCRIPTION OF THE EMBODIMENTS

0044The following explains an embodiment of the present invention with reference to <figref idref="DRAWINGS">FIGS. 1 to 11</figref>.

0045<figref idref="DRAWINGS">FIG. 2</figref> illustrates a longitudinal section of an image forming apparatus according to the present embodiment. As illustrated in <figref idref="DRAWINGS">FIG. 2</figref>, an image forming apparatus <b>1</b> includes: an image reading device (scanner) <b>2</b> for reading a document by use of a CCD (Charge Coupled Device) and the like and outputting an image signal; a printer <b>3</b> for forming (printing) an image on a sheet based on the image signal; and a sheet feeding desk device <b>4</b> for serially supplying sheets to the printer <b>3</b>.

0046The printer <b>3</b> includes three color photoconductor drums <b>10</b><i>a </i>respectively corresponding to magenta, cyan, and yellow and a black photoconductor drum <b>10</b><i>b </i>which is larger than each color photoconductor drum <b>10</b><i>a</i>. An optical unit (LSU) <b>12</b> writes electrostatic latent images on the photoconductor drums <b>10</b>. The writing is digitally controlled.

0047At the vicinity of each of the photoconductor drums <b>10</b>, there is provided a developing device <b>13</b> which contains corresponding developer out of magenta, cyan, yellow, and black, and develops an electrostatic latent image on the photoconductor drum <b>10</b>. In the present invention, developer is two-component developer which is a mixture of (i) carrier made of iron powder and the like and (ii) toner with predetermined density (e.g. 4 to 5%).

0048At the vicinity of each of the photoconductor drums <b>10</b>, in addition to the developing device <b>13</b>, there are provided known members in a Carlson process, such as a charger, a cleaner, a transfer device (used to transfer an image from the photoconductor drum <b>10</b> to a transfer belt <b>14</b>), and the like.

0049In the arrangement illustrated in <figref idref="DRAWINGS">FIG. 2</figref>, the transfer belt <b>14</b> is provided so as to be in contact with each of the photoconductor drums <b>10</b>. Toner images (visible images) formed on the respective photoconductor drums <b>10</b> are transferred onto the transfer belt <b>14</b> so as to serially overlap each other. Thereafter, a second transfer unit <b>15</b> transfers the image onto a paper supplied from a paper feeding desk device <b>4</b> including a plurality of paper feeding cassettes <b>20</b>. In a direction in which the paper having passed through the second transfer unit <b>15</b> is conveyed, there is provided a fixing device including a fixing roller <b>16</b>. The toner image transferred onto the paper is fixed onto the paper by passing through the fixing device.

0050The paper onto which the toner image has been fixed is then delivered to a space between the image reading device <b>2</b> and the printer <b>3</b> or inversely conveyed and delivered to the second transfer unit <b>15</b> again.

0051Above the transfer belt <b>14</b>, there are provided color toner bottles <b>17</b> which respectively contain magenta, cyan, and yellow, and two toner bottles <b>17</b><i>b </i>which are one size larger than the color toner bottle <b>17</b> and which contain black toner. Each of the toner bottles (supply device) <b>17</b> supplies toner contained therein to the developing device <b>13</b> corresponding to each of the toner bottles <b>17</b>. Each of the toner bottles <b>17</b> is rotated by a driving force transmitted from a toner motor (supply motor) (not shown) to each of the toner bottles <b>17</b>. Each of the toner bottles <b>17</b> supplies toner while being rotated.

0052Further, the toner bottle <b>17</b> is provided so as to be detachable from the image forming apparatus <b>1</b>. As such, when toner in the toner bottle <b>17</b> is consumed, it is possible to replace the toner bottle <b>17</b> with a new one. In the image forming apparatus <b>1</b>, the toner bottle has a cylindrical shape and is rotatable as illustrated in <figref idref="DRAWINGS">FIG. 11</figref>. An example of the cylindrical toner bottle is disclosed in Japanese Unexamined Patent Publication No. 317592/2004 (Tokukai 2004-317592; published on Nov. 11, 2004).

0053The toner bottle <b>17</b> includes a bottle main body <b>50</b> for containing toner and a supporting material <b>51</b> for supporting the bottle main body <b>50</b> so that the bottle main body <b>50</b> is rotatable. As indicated by an arrow R in <figref idref="DRAWINGS">FIG. 11</figref>, the bottle main body <b>50</b> is rotated so that an axis L <b>50</b> of the bottle main body <b>50</b> is a rotational axis. On the circumferential face of the bottle main body <b>50</b>, there is formed a groove <b>52</b> having an inclined shape. The groove <b>52</b> has a convex shape on the inner wall of the bottle main body <b>50</b>. When the bottle main body <b>50</b> is rotated, toner in the bottle main body <b>50</b> is guided by the groove <b>52</b> to a supply port. The toner bottle <b>17</b> having such a mechanism is stable in terms of the amount of toner supply per one rotation.

0054With reference to <figref idref="DRAWINGS">FIG. 1</figref>, the following details a process of the image forming apparatus <b>1</b> according to the present embodiment, in which process the amount of remaining toner is detected and a user is informed of the amount of remaining toner based on the result of detection. <figref idref="DRAWINGS">FIG. 1</figref> is a control block diagram illustrating essential parts of the image forming apparatus <b>1</b>.

0055As illustrated in <figref idref="DRAWINGS">FIG. 1</figref>, the image forming apparatus <b>1</b> includes a remaining toner amount detection section (remaining toner amount detection means) <b>31</b>, a magnetic permeability sensor <b>37</b>, a predetermined value setting section (predetermined value setting means) <b>39</b>, a correcting section (correcting means) <b>40</b>, an input section <b>38</b>, a remaining amount informing section (informing means, informing section) <b>41</b>, a display section <b>42</b>, and a machine stopping section <b>43</b>.

0056The remaining toner amount detection section <b>31</b> detects the amount of remaining toner in the toner bottle <b>17</b> and includes a toner supply amount calculation section (toner supply amount calculation means) <b>32</b>, a toner consumption amount calculation section (toner consumption amount calculation means) <b>33</b>, a toner density control section (toner density control means) <b>34</b>, an accumulated rotational time measurement section (toner supply amount calculation means, toner supply amount calculation section) <b>35</b>, and a pixel count section (toner consumption amount calculation means, toner consumption amount calculation section) <b>36</b>.

0057The remaining toner amount detection section <b>31</b> detects the amount of remaining toner based on the result of calculation carried out by the toner supply amount calculation section <b>32</b> until the amount reaches a first predetermined value. When the amount reaches the first predetermined value, the remaining toner amount detection section <b>31</b> detects the amount based on the result of calculation carried out by the toner consumption amount calculation section <b>33</b> until the amount reaches a second predetermined value. When the amount reaches the second predetermined value, the remaining toner amount detection section <b>31</b> detects the amount based on the result of control carried out by the toner density control section <b>34</b>.

0058The toner supply amount calculation section <b>32</b> calculates the amount of toner supplied from the toner bottle <b>17</b> to the developing device <b>13</b> based on the accumulated number of rotations of a toner motor which is measured by the accumulated rotational time measurement section <b>35</b>. Here, <figref idref="DRAWINGS">FIG. 3</figref> illustrates a relation between the amount of remaining toner in the toner bottle <b>17</b> and the amount of toner falling into the developing device <b>13</b> (corresponding to the amount of toner supply). As illustrated in <figref idref="DRAWINGS">FIG. 3</figref>, while the amount of remaining toner ranges from the initial remaining amount 360 g (full) to 100 g, the amount of falling toner is constant. When the amount of remaining toner is less than 100 g, the amount does not change linearly. This is because: as the amount of remaining toner drops, the amount of air included in toner increases, and thus the amount of toner supply becomes unstable.

0059Further, <figref idref="DRAWINGS">FIG. 4</figref> illustrates a relation between the rotational time of the toner motor and the amount of remaining toner in the toner bottle <b>17</b>. In this relation, too, the amount of remaining toner in the toner bottle <b>17</b> changes linearly while the amount ranges from 360 g (full) to 100 g, but does not change linearly when the amount is less than 100 g.

0060Therefore, in the example illustrated in <figref idref="DRAWINGS">FIGS. 3 and 4</figref>, while the amount of remaining toner is 100 g or more, accumulation of the time during which the toner motor is rotated (in other words, accumulation of the number of rotations of the toner motor) allows calculation of the amount of toner supplied from the toner bottle <b>17</b> to the developing device <b>13</b>. Such calculation of the amount of toner supply based on the accumulated rotational time of the toner motor is exact as well as easy.

0061The toner consumption amount calculation section <b>33</b> calculates the amount of toner consumed by forming images based on image information. Here, the amount of toner consumption is calculated based on the result of pixel count carried out by the pixel count section <b>36</b>. The pixel count section <b>36</b> performs pixel count of an image signal having been subject to a half tone correction process or the like while multiplying the image signal by a weight coefficient with respect to each of CMYK signals by each pixel. Calculation carried out by the pixel count section <b>36</b> and the toner consumption amount calculation section <b>33</b> with respect to the amount of toner consumption is detailed later.

0062The toner density control section <b>34</b> controls toner density in the developing device <b>13</b> based on the magnetic permeability of the developer which is detected by the magnetic permeability sensor <b>37</b>. As is already explained, a conventional image forming apparatus using two-component developer performs a control for supplying toner from the toner bottle <b>17</b> to the developing device <b>13</b> based on the magnetic permeability of developer in the developing device <b>13</b> and thus keeping the toner density in the developing device <b>13</b> in a constant value (this control is referred to as “ATC” hereinafter).

0063Here, when the magnetic permeability rises and the toner density becomes equal to a lower limit or less, the toner density control section <b>34</b> causes the toner motor to rotate for a predetermined time T₁, thereby supplying toner from the toner bottle <b>17</b>. Note that, the present invention may be arranged so that: an upper limit of toner density is also specified and when the toner density is less than the lower limit, the toner motor is rotated until the toner density reaches the upper limit of the toner density, thereby supplying toner from the toner bottle <b>17</b>.

0064The remaining toner amount detection section <b>31</b> detects that toner will soon run out, namely, “near end”, when a process is repeated in which: the toner density control section <b>34</b> performs ATC and rotates the toner motor for a predetermined time, the toner density again has a value equal to the limit or less after a short interval, and the toner density control section <b>34</b> performs ATC again.

0065Further, the remaining toner amount detection section <b>31</b> detects that toner runs out when the toner density continues to have a value equal to the lower limit or less after the toner density control section <b>34</b> performs ATC and rotates the toner motor for a predetermined time and the toner density still continues to have a value equal to the lower limit or less after a predetermined time T₂(e.g. 5 seconds) passes.

0066The first predetermined value at which the method for detecting the amount of remaining toner is changed from a method based on the result of calculation carried out by the toner supply amount calculation section <b>32</b> to a method based on the result of calculation carried out by the toner consumption calculation section <b>33</b> is a value within a region where the amount of remaining toner in the toner bottle <b>17</b> changes linearly in accordance with the accumulated rotational time (accumulated number of rotations) of the toner motor. The first predetermined value is preferably the lower limit of the region. In the example illustrated in <figref idref="DRAWINGS">FIGS. 3 and 4</figref>, the first predetermined value should be 100 g.

0067The second predetermined value at which the method for detecting the amount of remaining toner is changed from a method based on the result of calculation carried out by the toner consumption calculation section <b>33</b> to a method based on the result of control carried out by the toner density control section <b>34</b> is a value which allows detection of the amount of remaining toner based on the result of control carried out by the toner density control section <b>34</b> even when an error occurs in calculation carried out by the toner consumption amount calculation section <b>33</b>. In the present embodiment, the second predetermined value is equal to a later-mentioned limit amount W_L(third predetermined value) for determining a timing at which a message for urging the user to prepare toner is displayed.

0068The remaining amount informing section <b>41</b> causes the display section <b>42</b> to display information concerning the amount of remaining toner in the toner bottle <b>17</b> based on detection carried out by the remaining toner amount detection section <b>31</b> with respect to the amount of remaining toner. Here, according to the detected amount of remaining toner, three items of information: (i) a new toner bottle <b>17</b> for exchange should be prepared, (ii) the toner bottle <b>17</b> in use should be exchanged, and (iii) toner runs out, are displayed.

0069When the amount of remaining toner detected by the remaining toner amount detection section <b>31</b> reaches the limit amount W_L(third predetermined value), the remaining amount informing section <b>41</b> causes the display section <b>42</b> to display a message such as “please prepare a new toner bottle”. It is preferable that the limit amount W_Lis set with respect to each user. The limit amount W_Lshould be set so as to have a value obtained by multiplying (i) the amount of toner consumption per a day with respect to a user by (ii) the number of days taken for the user to obtain a new toner bottle <b>17</b> with which the user exchanges the toner bottle <b>17</b> in use. As a result, it is possible to display the message at a suitable timing.

0070Further, when the remaining toner amount detection section <b>31</b> detects that toner is near end, the remaining amount informing section <b>41</b> causes the display section <b>42</b> to display a message such as “please exchange the toner bottle”.

0071Further, when the remaining toner amount detection section <b>31</b> detects that toner runs out, the remaining amount informing section <b>41</b> causes the display section <b>42</b> to display a message such as “toner runs out”.

0072When the remaining toner amount detection section <b>31</b> detects that toner runs out, the machine stopping section <b>43</b> stops operation of the image forming apparatus <b>1</b>.

0073The input section <b>38</b> allows external setting of the first and second predetermined values, the limit amount W_L, a second limit amount W_P, and the like. The first and second predetermined values vary with respect to each image forming apparatus and vary because of version up/down of the toner bottle. Therefore, by allowing such external setting, it is possible to handle variation with respect to each image forming apparatus or version up/down of the toner bottle. Further, because the limit amount W_Land the second limit amount W_Pare different with respect to each user, by allowing a service person or the like to suitably set the amounts via the input section <b>38</b>, it is possible to inform the message at a more suitable timing.

0074The predetermined value setting section <b>39</b> sets the limit amount W_L(third predetermined value) based on calculation. To be specific, the predetermined value setting section <b>39</b> includes a consumption amount/day calculation section (consumption amount/day calculation means) and a predetermined value calculation section (predetermined value calculation means). The consumption amount/day calculation section subtracts the first predetermined value from the initial amount of toner in the toner bottle <b>17</b> and divides thus obtained value by elapsed days which have elapsed from the day when the toner bottle <b>17</b> was exchanged to the day when the amount of remaining toner reaches the first predetermined value, thereby calculating the consumption amount per day. The predetermined value calculation section multiplies (i) the consumption amount/day calculated by the consumption amount/day calculation section by (ii) preparation days having been set with respect to each user, thereby calculating the limit amount W_L.

0075The preparation days here are days taken for the user to prepare a toner bottle <b>17</b> for exchange. The preparation days as well as the initial amount of toner can be input via the input section <b>38</b>. On the other hand, the elapsed days can be obtained by calculating the number of days having passed from the day when the toner bottle <b>17</b> was exchanged (the days are stored in a memory or the like (not shown)) to the day when the amount of remaining toner reaches the first predetermined value.

0076Installation of the predetermined value setting section <b>39</b> allows the user to be informed of the message at a more suitable timing, and thus it is possible to urge the user to prepare toner exactly at a timing desired by the user (including preparation days) in consideration of the amount of toner recently consumed by the user.

0077The correcting section <b>40</b> corrects the calculated amount of toner consumption, which amount has been calculated by the toner consumption amount calculation section <b>33</b>. While the amount of toner has not yet reached the first predetermined amount, the correcting section <b>40</b> causes the pixel count section <b>36</b> and the toner consumption amount calculation section <b>33</b> to calculate the amount of toner consumption as well as causes the toner supply amount calculation section <b>32</b> to calculate the amount of toner supply, and the correcting section <b>40</b> causes the toner consumption amount calculation section <b>33</b> (alternatively, the pixel count section <b>36</b>, or both) to correct the amount of toner consumption on the basis of the amount of toner supply calculated by the toner supply amount calculation section <b>32</b>.

0078For example, in a case where calculation carried out by the toner supply amount calculation section <b>32</b> so as to obtain the amount of toner supply indicates 250 g, while calculation carried out by the toner consumption amount calculation section <b>33</b> so as to obtain the amount of toner consumption indicates 260 g, the toner consumption amount calculation section <b>33</b> is caused to correct the calculated amount of toner consumption so that the calculated amount of toner consumption is 250 g which is equal to the calculated amount of toner supply.

0079<figref idref="DRAWINGS">FIG. 5</figref> schematically illustrates (i) switching of methods for detecting the amount of remaining toner by the remaining toner amount detection section <b>31</b> and (ii) timing at which the remaining amount informing section <b>41</b> causes the amount of remaining toner and information concerning the amount of remaining toner to be displayed. In <figref idref="DRAWINGS">FIG. 5</figref>, the vertical axis indicates the amount of remaining toner and the lateral axis indicates time.

0080As illustrated in <figref idref="DRAWINGS">FIG. 5</figref>, from a time when remaining toner is fully contained to a time when the remaining toner is 100 g corresponding to the first predetermined value, the amount of the remaining toner is calculated by the toner supply amount calculation section <b>32</b>. When the remaining toner is less than 10 g, the amount of the remaining toner is calculated by the toner consumption amount calculation section <b>33</b>. Thereafter, when: the amount of the remaining toner is further reduced and reaches the limitation amount W_Lcorresponding to the third predetermined value, the amount of the remaining toner is detected based on ATC and a message for urging the user to prepare new toner (NNE) is displayed. Thereafter, when “near end” is detected by the remaining toner amount detection section <b>31</b>, a message for urging the user to exchange toner (NE) is displayed. Further, when “toner runs out” is detected, a message indicating “toner empty” is displayed.

0081Here, with reference to <figref idref="DRAWINGS">FIG. 6</figref>, the following explains calculation of the amount of toner consumption based on the result of pixel count carried out by the toner consumption amount calculation section <b>33</b>.

0082<figref idref="DRAWINGS">FIG. 6</figref> is a control block diagram illustrating an image process carried out by the image forming apparatus <b>1</b>. Here, a control system of the image process is constituted of an input signal process section <b>110</b>, a region separating process section <b>120</b>, a color correcting/black generating process section <b>130</b>, a variable zoom power process section <b>140</b>, a space filter process section <b>150</b>, a half tone correcting process section <b>160</b>, the pixel count section <b>36</b>, and the toner consumption amount calculation section <b>33</b>.

0083The image process is shortly explained. A digital input image signal of a document read out by a scanner or the like is inputted to the input signal process section <b>110</b> and is subject to (i) a pre-process carried out before subsequent image processes, (ii) input gamma correction in image adjustment, (iii) conversion, and the like. Next, the image signal is inputted to the region separating process section <b>120</b> and is subject to a region judgment process for judging a character region, a halftone dot picture region, and the like, and an identification signal (region separating identification signal) corresponding to each region is added to the image signal. The region separating identification signal is used when the space filter process section <b>150</b> and the half tone correcting process section <b>160</b>, which perform subsequent processes, perform a process specific to each region. Examples of the process specific to each region include a smoothing filter process for a halftone dot region, an edge emphasizing filter process for a character region, and a process for changing half tone gamma characteristics into characteristics having more sharper difference between light and dark.

0084A color correcting/black generating process performed in the subsequent color correcting/black generating process section <b>130</b> is a process which is necessary in a case where the image forming apparatus is capable of forming color images. The color correcting/black generating process converts the image signals of RGB transmitted from the region separating process section <b>120</b> into image signals of CMYK (cyan, magenta, yellow, and black) which are to be finally outputted.

0085The image signal having been converted into CMYK is subject to a variable power process carried out by the variable zoom power process section <b>140</b>, and then is inputted to the space filter process section <b>150</b>. The space filter process section <b>150</b> selects, out of a space filter table, a space filter corresponding to the region separating identification signal, a setting state of an image mode, or the like, and performs a space filter process with respect to an image signal having been converted to CMYK. Note that, the space filter table is a table group of filter coefficients which are referred to in performing the space filter process, and any table group can be selected according to situation. The half tone correcting process section <b>160</b> corrects half tone gamma characteristics so as to correct output characteristics of an engine section.

0086Further, the image signal having been subject to the half tone correcting process is inputted to the pixel count section <b>36</b> and accumulated by a counter while being weighted with respect to each of CMYK signals by each pixel. Then, the output image signal is outputted to an engine output side of an LSU or an LED. The toner consumption amount calculation section <b>33</b> calculates the amount of toner consumption with respect to each color based on the value of pixel counts accumulated by the pixel count section <b>36</b>.

0087Next, the following details the calculation of the amount of toner consumption. Note that, the process described below is performed with respect to each of CMYK (with respect to each of inputted CMYK signals).

0088The pixel count section <b>36</b> performs later-mentioned pixel count with respect to an inputted multi-valued image. As illustrated in <figref idref="DRAWINGS">FIG. 6</figref>, the pixel count section <b>36</b> includes a count section <b>171</b>, a weight calculation section <b>172</b>, a weight coefficient table <b>173</b>, and an accumulation section <b>174</b>.

0089The count section (count means) <b>171</b> counts the inputted multi-valued image (for example, an image having multi-gradations such as 16 gradations or 256 gradations) by each pixel. Namely, the count section <b>171</b> counts an input signal value (gradation) for each pixel constituting a multi-valued image. For example, in a case of 16 gradations whose input signal value ranges from 0 to 15, the count section <b>171</b> counts 0 to 15.

0090The weight calculation section (weight calculation means) 172 weights each pixel, when pixels are counted by the count section <b>171</b>. To be specific, the weight calculation section <b>172</b> acquires, from the weight coefficient table <b>173</b>, a weight coefficient corresponding to an input signal value for each pixel, and multiplies an input signal value by the acquired weight coefficient. The weight coefficient table <b>173</b> stores a weight coefficient corresponding to each pixel input value at a time when the weight calculation section <b>172</b> weights an input signal value. In this way, the pixel count section <b>36</b> performs pixel count for each pixel, by use of the count section <b>171</b>, the weight calculation section <b>172</b>, and the weight coefficient table <b>173</b>.

0091Next, accumulation of pixel counts for each pixel is performed by the accumulation section (accumulation means) <b>174</b>. Namely, the accumulation section <b>174</b> accumulates calculation values of all the pixels of the inputted multi-valued image, each of the calculation values being obtained by the weight calculation section <b>172</b> multiplying the input signal value by the weight coefficient. In this way, the toner consumption amount calculation section <b>33</b> calculates the amount of toner consumption of an outputted image based on the accumulated value of pixel counts calculated by the pixel count section <b>36</b>.

0092<figref idref="DRAWINGS">FIG. 7</figref> illustrates an example of weight coefficients stored in the weight coefficient table <b>173</b>. In the example, the input signal value has 16 values, namely, the input signal value ranges from 0 to 15. In <figref idref="DRAWINGS">FIG. 7</figref>, there are provided four areas (areas 1 to 4) each corresponding to an input signal value having different toner consumption, and a weight coefficient is assigned to each area. When pixel count is performed, the weight coefficient assigned to each area is selected according to each input signal value ranging from 0 to 15 and weighting is performed by using the selected weight coefficient.

0093<figref idref="DRAWINGS">FIG. 8</figref> illustrates a relation between (i) the signal input values in a weight coefficient table divided into four areas and (ii) weight coefficients corresponding to the signal input values. As illustrated in <figref idref="DRAWINGS">FIG. 8</figref>, the sum of the areas of rectangular portions is substantially equal to the area of a curve indicative of the consumption amount characteristics, so that it is possible to predict and calculate the amount of toner consumption based on the accumulated value of pixel count after weighting.

0094Note that, in the example illustrated in <figref idref="DRAWINGS">FIG. 7</figref>, the weight coefficients stored in the weight coefficient table <b>173</b> are fixed values. However, the weight coefficient may be changed so that the amount of toner consumption calculated by the toner consumption calculation section <b>33</b> corresponds to the actual amount of toner consumption.

0095Further, the present invention may be arranged so that: a dot count section for counting, based on image information, the number of times printed dots are formed is provided instead of the pixel count section <b>36</b>, and the toner consumption amount calculation section <b>33</b> calculates the amount of toner consumption based on the result of count carried out by the dot count section. In a case where the number of dots is counted, too, a predetermined weight coefficient is multiplied by the number. As disclosed in Japanese Unexamined Patent Publication No. 163553/2004 and Japanese Unexamined Patent Publication No. 163554/2004, by changing the weight coefficient according to use history of toner or changing the weight coefficient according to three classifications of dots such as an isolated dot, two-continuous dots, and three-continuous dots, it is possible to calculate the amount of toner consumption more precisely.

0096With reference to flowcharts in <figref idref="DRAWINGS">FIGS. 9 and 10</figref>, the following explains a process of the image forming apparatus <b>1</b>, in which process the amount of remaining toner is detected and the user is informed of information indicative of the amount of remaining toner based on the result of the detection. Here, an example in which the predetermined value setting section <b>39</b> sets the limit amount W_Lis explained.

0097The remaining toner amount detection section <b>31</b> and the predetermined value setting section <b>39</b> determine whether the toner bottle <b>17</b> is new or not (S<b>1</b>). When the toner bottle <b>17</b> is new, the remaining toner amount detection section <b>31</b> and the predetermined value setting section <b>39</b> perform initial setting (S<b>2</b>). The predetermined value setting section <b>39</b> stores the present date as the day of exchange of the toner bottle <b>17</b> in a memory (not shown) and causes a flag for indicating whether a predetermined value is set or not to be “0” indicating that a predetermined value is not set. Further, the remaining toner amount detection section <b>31</b> causes accumulated rotational time (Σ time) of the accumulated rotational time measurement section <b>35</b> to be “0”.

0098Next, the remaining toner amount detection section <b>31</b> causes the toner supply amount calculation section <b>32</b> to calculate the amount of toner supply. Each time when the toner motor is rotated for a predetermined time (T₁second) in ATC (S<b>3</b> and S<b>4</b>) carried out by the toner density control section <b>34</b>, the accumulated rotational time measurement section <b>35</b> increases the accumulated rotational time (Σ time) by T₁(S<b>5</b>). The remaining toner amount detection section <b>31</b> determines whether the accumulated rotational time measured by the accumulated rotational time measurement section <b>35</b> reaches the upper limit or not (S<b>6</b>).

0099The upper limit of the accumulated rotational time (Σ time) in S<b>6</b> corresponds to the accumulated rotational time with which toner is supplied so that the amount of remaining toner in the toner bottle <b>17</b> becomes the first predetermined value. For example, in a case where the initial amount of toner in the toner bottle <b>17</b> is 360 g and the first predetermined value is 100 g, the upper limit of the rotational time is a time with which toner (360−100=260 g) is supplied.

0100When it is judged that the accumulated rotational time (Σ time) reaches the upper limit, the remaining toner amount detection section <b>31</b> changes the method for detecting the amount of remaining toner from detection carried out by the toner supply amount calculation section <b>32</b> to detection carried out by the toner consumption amount calculation section <b>33</b> and informs the change to the predetermined value setting section <b>39</b>. Note that, when the accumulated rotational time (Σ time) does not reach the upper limit, the process goes back to S<b>3</b>.

0101When the remaining toner amount detection section <b>31</b> judges that the accumulated rotational time reaches the upper limit, the predetermined value setting section <b>39</b> judges whether the flag is “0” or not. When the flag is “0”, the process goes to S<b>8</b> and a predetermined value is set based on calculation. When the flag is not “0”, because the predetermined value has already been set based on calculation, the predetermined value is not set based on the calculation in S<b>8</b>.

0102In S<b>8</b>, the consumption amount/day calculation section calculates, based on the number of days having passed since the day when the toner bottle was exchanged, the number of days Σ Day taken for the amount of toner to have the first predetermined value, and divides the amount of toner supply by the number of days, thereby obtaining the amount of consumption per day (the amount of consumption/day). Next, the predetermined value calculation section multiplies the calculated amount of consumption/day by preparation days having been set with respect to each user, thereby obtaining the limit amount W_Lwhich is the third predetermined value. When the predetermined value is set, the predetermined value setting section <b>39</b> causes the flag to be “1”.

0103Next, the remaining toner amount detection section <b>31</b> causes the toner consumption amount calculation section <b>33</b> to calculate the amount of toner consumption dw (S<b>9</b>), subtracts the amount of toner consumption dw from the amount of remaining toner W₁(equal to the first predetermined value) (S<b>10</b>), and judges whether the amount of remaining toner W₁reaches the limit amount W_Lor not (S<b>11</b>). When the amount of remaining toner W₁does not reach the limit amount W_L, the process goes back to S<b>9</b>.

0104On the other hand, when the amount of remaining toner W₁reaches the limit amount W_L, the remaining toner amount detection section <b>31</b> informs the remaining amount informing section <b>41</b> that the amount of remaining toner W₁reaches the limit amount W_L, and the remaining amount informing section <b>41</b> causes a message for urging preparation of new toner to be displayed (S<b>12</b>). Further, when the amount of remaining toner W₁reaches the limit amount W_L, the remaining toner amount detection section <b>31</b> changes detection of remaining toner from detection carried out by the toner consumption amount calculation section <b>33</b> to detection of “near end” or “toner runs out” which is carried out by the toner density control section <b>34</b> (S<b>13</b>).

0105The remaining toner amount detection section <b>31</b> judges whether toner is near end or not (S<b>14</b>), and repeats the process until the remaining toner amount detection section <b>31</b> judges that the toner is near end. On the other hand, when the remaining toner amount detection section <b>31</b> judges that the toner is near end, the remaining toner amount detection section <b>31</b> informs the remaining amount informing section <b>41</b> that “near end” is detected, and the remaining amount informing section <b>41</b> causes a message for urging exchange of the toner bottle <b>17</b> to be displayed (S<b>15</b>).

0106Thereafter, the toner density control section <b>34</b> judges whether the toner runs out or not (S<b>16</b>), and repeats the process until the toner density control section <b>34</b> judges that the toner runs out. Here, the toner density control section <b>34</b> judges whether toner density continues to be less than the limit value for a predetermined time (T₂) or more. When the toner density continues to be less than the limit value for the predetermined time (T₂) or more, the remaining toner amount detection section <b>31</b> judges that the toner runs out. When the remaining toner amount detection section <b>31</b> judges that the toner runs out, the remaining toner amount detection section <b>31</b> informs the remaining amount informing section <b>41</b> and the machine stopping section <b>43</b> that the toner runs out.

0107When the remaining toner amount detection section <b>31</b> judges that the toner runs out, the remaining amount informing section <b>41</b> causes a message indicating that toner runs out to be displayed, and the machine stopping section <b>43</b> stops the image forming apparatus <b>1</b> (S<b>17</b>).

0108As described above, in the image forming apparatus <b>1</b>, the remaining toner amount detection section <b>31</b> detects the amount of remaining toner by using the result of calculation carried out by the toner supply amount calculation section <b>32</b> based on accumulated rotational time of the toner motor in a region where the amount of remaining toner in the supply device is not less than a predetermined amount and changes linearly in accordance with the number of rotations or the rotational time of the supply motor and thus stabilizes the amount of toner supply (until the amount of remaining toner reaches the first predetermined value). Further, the remaining toner amount detection section <b>31</b> detects the amount of remaining toner by using the result of calculation carried out by the toner consumption amount calculation section <b>33</b> based on pixel counts in a region where the amount of remaining toner in the supply device gets small and the amount of toner supply gets uneven (from the first predetermined value to the second predetermined value). Further, the remaining toner amount detection section <b>31</b> detects the amount of remaining toner by using the result of ATC carried out by the toner density control section <b>34</b> in a region where toner is near end.

0109This allows detection of the amount of remaining toner according to actually remaining toner. As a result, it is possible to exactly detect the amount of remaining toner from a time when toner is fully contained to a time when toner runs out without including a special remaining toner detection device. Further, unlike detection of the amount of remaining toner carried out only by ATC, it is possible to chronologically detect the amount of remaining toner from the time when toner is fully contained to the time when toner runs out, so that it is possible to easily inform the user of information concerning toner at a suitable timing by use of the remaining amount informing section <b>41</b> and the like.

0110Further, in the present embodiment, the second predetermined value with which the method for detecting the amount of remaining toner is changed from a method based on calculation carried out by the toner consumption amount calculation section <b>33</b> to a method based on control carried out by the toner density control section <b>34</b> is the same as the limit amount W_L(third predetermined value). However, the second predetermined value may be set as the second limit amount W_Pwith respect to each user. The second limit amount W_Pmay be set so as to have a value which allows, for example, 50 sheets of images to be formed.

0111When the second predetermined value is set as the second limit amount W_P, it is preferable that the second limit amount W_Pcan be inputted via the input section <b>38</b> and the predetermined amount setting section <b>39</b> can set the second limit amount W_Pbased on calculation. Namely, the accumulated number of sheets after the toner bottle <b>17</b> is exchanged is measured, the value obtained by subtracting the first predetermined value from the initial amount of toner in the toner bottle <b>17</b> is divided by the accumulated number of sheets, thereby calculating the amount of toner consumption per sheet (consumption/sheet) in a region where the amount of remaining toner in the toner bottle <b>17</b> changes linearly in accordance with the accumulated number of rotations of the supply motor. Then, thus calculated amount of toner consumption/sheet is multiplied by the limited number of sheets having been set with respect to each user, thereby calculating the second limit amount W_P.

0112In the detection of the amount of remaining toner based on the result of control carried out by the toner density control section <b>34</b>, the amount of reduced toner is not directly detected. Therefore, in a case where the limit amount W_L(third predetermined value) is set and a message urging preparation of toner is displayed, it is necessary to display the message at the same time or before the detection of the amount of remaining toner switches to the detection based on the result of control carried out by the toner density control section <b>34</b>. As such, it is preferable that the second limit amount W_Pis not more than the limit amount W_L(third predetermined value).

0113The invention being thus described, it will be obvious that the same way may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

0114Note that, each section (except for the input section and the display section) included in the image forming apparatus <b>1</b> according to the present embodiment is a functional block realized in such a manner that: operation means such as a CPU (Central Processing Unit) executes a program stored in storage means such as a ROM (Read Only Memory), RAM (Random Access Memory), and the like, and controls input means (input section) such as a keyboard, output means (display section) such as a display, or communication means such as an interface circuit.

0115Therefore, a computer having these means reads a storage medium for storing the program and executes the program, thereby realizing functions and processes of the image forming apparatus <b>1</b> according to the present invention.

0116Such a computer program storage medium may be a memory (not shown), such as a ROM, so that the process is executable on a microcomputer. Alternatively, a program medium may be used which can be read by inserting the storage medium in an external storage device (program reader device; not shown).

0117In addition, in either of the cases, it is preferable if the contained program is accessible to a microprocessor which will execute the program. Further, it is preferable if the program is read, and the program is then downloaded to a program storage area of a microcomputer where the program is executed. Assume that the program for download is stored in a main body device in advance.

0118In addition, the program medium is a storage medium arranged so that it can be separated from the main body. Examples of such a program medium include a tape, such as a magnetic tape and a cassette tape; a magnetic disk, such as a flexible disk and a hard disk; a disc, such as a CD/MO/MD/DVD; a card, such as an IC card (inclusive of a memory card); and a semiconductor memory, such as a mask ROM, an EPROM (erasable programmable read only memory), an EEPROM (electrically erasable programmable read only memory), or a flash ROM. All these storage media hold a program in a fixed manner.

0119Alternatively, if a system can be constructed which can connects to the Internet or other communications network, it is preferable if the program medium is a storage medium carrying the program in a flowing manner as in the downloading of a program over the communications network.

0120Further, when the program is downloaded over a communications network in this manner, it is preferable if the program for download is stored in a main body device in advance or installed from another storage medium.

0121As described above, the image forming apparatus according to the present invention is an image forming apparatus, which uses two-component developer constituted of toner and carrier and includes toner density control means for supplying the toner from a supply device to a developing device on the basis of magnetic permeability of the developer so as to cause toner density in the developing device to be constant, the image forming apparatus including remaining toner amount detection means for detecting the amount of remaining toner in the supply device, wherein the remaining toner amount detection means includes: toner supply amount calculation means for calculating the amount of toner supply on the basis of the accumulated number of rotations of a supply motor which is rotated so as to supply toner from the supply device to the developing device; toner consumption amount calculation means for calculating the amount of toner consumed by forming an image on the basis of image information; and the toner density control means, and the remaining toner amount detection means detects the amount of remaining toner on the basis of (i) the result of calculation carried out by the toner supply amount calculation means till the amount of remaining toner in the supply device reaches a first predetermined value, (ii) the result of calculation carried out by the toner consumption amount calculation means from a time when the amount of remaining toner in the supply device reaches the first predetermined value till the amount of remaining toner in the supply device reaches a second predetermined value, and (iii) the result of control carried out by the toner density control means from a time when the amount of remaining toner in the supply device reaches the second predetermined value.

0122With the arrangement, the amount of remaining toner in the supply device is detected on the basis of (i) the amount of toner supply which is calculated by the toner supply amount calculation means based on the accumulated number of rotations of the supply motor till the amount of remaining toner in the supply device reaches the first predetermined value, (ii) the amount of toner consumption which is calculated by the toner consumption amount calculation means based on the image information from the time when the amount of remaining toner in the supply device reaches the first predetermined value till the amount of remaining toner in the supply device reaches the second predetermined value, and (iii) the result of control carried out by the toner density control means from the time when the amount of remaining toner in the supply device reaches the second predetermined value.

0123Namely, the amount of remaining toner is detected based on the accumulated number of rotations of the toner motor in a region where the amount of remaining toner in the supply device is not less than a predetermined amount and changes linearly in accordance with the number of rotations or the rotational time of the supply motor and thus stabilizes the amount of toner supply. Further, the amount of remaining toner is detected by expecting the amount of consumed toner based on the image information in a region where the amount of remaining toner in the supply device gets small and the amount of toner supply gets uneven. Further, the amount of remaining toner is detected by using the result of control carried out by the conventional toner density control means in a region where the amount of toner is near end.

0124As a result, it is possible to detect the amount of toner according to actually remaining toner, and accordingly it is possible to exactly detect the amount of remaining toner from a time when toner is fully contained to a time when toner runs out without providing a special remaining toner detection device.

0125Further, unlike the detection carried out only by ATC with respect to the amount of remaining toner, it is possible to chronologically detect the amount of remaining toner from a time when toner is fully contained to a time when toner runs out, so that it is easy to inform the user of information concerning toner at a suitable timing.

0126The first predetermined value can be set to a value within a region where the amount of remaining toner in the supply device changes linearly in accordance with the accumulated number of rotations of the supply motor and the second predetermined value can be set to a value which allows detection of the amount of remaining toner on the basis of the result of the control carried out by the toner density control means even when an error occurs in the calculation carried out by the toner consumption amount calculation means.

0127Further, the image forming apparatus according to the present invention may be arranged so that: a third predetermined value is set in accordance with the amount of used toner per days taken for a user to obtain a supply device for exchange, and there is provided informing means (an informing section) which causes a display section to inform a user that preparation of toner is necessary when detection carried out by the remaining toner amount detection means with respect to the amount of remaining toner shows that the amount of remaining toner in the supply device reaches the third predetermined value.

0128With the arrangement, when the amount of remaining toner reaches the third predetermined value which is set in accordance with the amount of used toner per days taken for the user to obtain a supply device for exchange, the informing means causes the display section to urge preparation of toner, so that the user can prepare the next toner at a suitable timing and accordingly it is possible to prevent reduction of an operation rate of the image forming apparatus.

0129The image forming apparatus may be arranged so as to include correcting means for causing the toner consumption amount calculation means to calculate the amount of toner consumption as well as causing the toner supply amount calculation means to calculate the amount of toner supply while the amount of remaining toner in the supply device has not yet reached the first predetermined value, so as to correct the toner consumption amount calculation means on the basis of the result of the calculation carried out by the toner supply amount calculation means with respect to the amount of toner supply.

0130The toner supply amount calculation means highly accurately carries out calculation in a region where the amount of remaining toner in the supply device changes linearly in accordance with the number of rotations and the rotational time of the supply motor. In the arrangement, by use of the high accuracy, the toner consumption amount calculation means is corrected based on the result of calculation carried out by the toner supply amount calculation means with high accuracy, so that it is possible to increase accuracy in calculating the amount of toner consumption carried out by the toner consumption amount calculation means.

0131The image forming apparatus according to the present invention may be arranged so that the toner consumption amount calculation means counts, based on the image information, how many times printing dots are formed, so as to calculate the amount of toner consumption.

0132Further, the image forming apparatus according to the present invention may be arranged so that: the toner consumption amount calculation means performs an image process and a correction process with respect to the image information in a digital manner and performs pixel count of an input multi-valued image so as to calculate the amount of toner consumption, and the toner consumption amount calculation means includes count means (count section) for counting an input signal value of the input multi-valued image with respect to each pixel, a weight coefficient table for storing a weight coefficient corresponding to the input signal value, and weight calculation means (calculation section) for acquiring the weight coefficient corresponding to the input signal value from the weight coefficient table and performs weighting with respect to each pixel when the count means counts the input signal value.

0133With the arrangement, it is possible to perform weighting in accordance with gradations of image information unlike calculation of the amount of toner consumption by counting formed dots, so that it is possible to calculate the amount of toner consumption with higher accuracy.

0134Further, the image forming apparatus according to the present invention may be arranged so as to include an input section which allows external setting of the first, second, and third predetermined values.

0135The first and second predetermined values vary with respect to each image forming apparatus and vary because of version up/down of the supply device. Therefore, by allowing such external setting, it is possible to handle variation with respect to each image forming apparatus or version up/down of the supply device. Further, because the third predetermined value is different with respect to each user, by allowing the third predetermined value to be suitably set via the input section, it is possible to inform the user of the message at a timing suitable for each user.

0136Further, the image forming apparatus according to the present invention may be arranged so that: the image forming apparatus includes predetermined value setting means (predetermined value setting section) for setting the third predetermined value on the basis of calculation, and the predetermined value setting means includes (i) consumption amount/day calculation means (consumption amount/day calculation section) for subtracting the first predetermined value from an initial amount of toner in the supply device and dividing thus obtained value by days which have passed from a day when the supply device was exchanged to a day when the amount of remaining toner reaches the first predetermined value, so as to obtain an amount of toner used by the user per day, and (ii) predetermined value calculation means (predetermined value calculation section) for multiplying consumption amount/day calculated by the consumption amount/day calculation means by preparation days inputted with respect to each user, so as to calculate the third predetermined value.

0137With the arrangement, the consumption amount/day calculation section calculates the amount of toner consumption per day and the predetermined value calculation section calculates the third predetermined value by multiplying the amount of toner consumption per day calculated by the consumption amount/day calculation section by the preparation days which are set with respect to each user. As a result, the timing for informing the user of the message gets more suitable, so that it is possible to urge the user to prepare new toner at a timing desired by the user (including preparation days).

0138The image forming apparatus according to the present invention may be arranged so that: the supply device includes a cylindrical container which contains the toner and which is disposed in a lateral manner, and the container is rotated so that an axis of the container is a rotational axis, so as to supply the toner from an opening provided on a cylindrical face of the container to the developing device.

0139The supply device having such a rotation mechanism is stable in terms of the amount of toner supply per one rotation. Therefore, when the supply device is used in the arrangement in which the amount of remaining toner is detected based on the amount of toner supply obtained from the accumulated number of rotations of the supply motor, it is possible to detect the amount of remaining toner with high accuracy.

0140The method according to the present invention for detecting the amount of remaining toner is a method for detecting the amount of remaining toner in a supply device applied to an image forming apparatus that uses two-component developer constituted of toner and carrier and that includes toner density control means for supplying the toner from the supply device to a developing device on the basis of magnetic permeability of the developer so as to cause toner density in the developing device to be constant, the method including the steps of (i) detecting the amount of remaining toner in the supply device on the basis of the accumulated number of rotations of the supply motor which supplies the toner from the supply device to the developing device in a region where the amount of remaining toner in the supply device is large and changes linearly in accordance with the accumulated number of rotations of the supply motor, (ii) detecting the amount of remaining toner in the supply device on the basis of the amount of toner consumed by forming an image on the basis of image information in a region where the amount of remaining toner in the supply device is small and does not change linearly in accordance with the accumulated number of rotations of the supply motor, and (iii) detecting the amount of remaining toner in the supply device on the basis of the result of control carried out by the toner density control means in a region where the amount of remaining toner is substantially 0.

0141In the method for detecting the amount of remaining toner as well as in the image forming apparatus already explained above, it is possible to detect the amount of remaining toner according to actually remaining toner, and accordingly it is possible to exactly detect the amount of remaining toner from a time when toner is fully contained to a time when toner runs out without providing a special remaining toner detection device and it can be easily realized to inform the user of information concerning toner at a suitable timing.